Collimation System
From GlueXWiki
The GlueX active collimator consists of 8 separate tungsten wedges placed symmetrically in two concentric rings around a 5-mm diameter clearance hole. It can be placed over any primary collimator aperture that is 5mm in diameter or smaller, and provide 8 independent signals which come into balance when the photon beam spot is properly centered on the collimator aperture. The wedges are mounted as shown inside a cylinder made of boron nitride, a white soft ceramic material that is an excellent insulator as well as being machinable and mechanically robust. The placement of the wedges on the boron nitride substrate are shown below.